[PATCH 2/5] xfs: cross-reference rmap records with ag btrees

Darrick J. Wong
2022-12-30T22:52:28Z

Strengthen the rmap btree record checker a little more by comparing
OWN_FS and OWN_LOG reverse mappings against the AG headers and internal
logs, respectively.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/Makefile | 2 -
fs/xfs/scrub/bitmap.c | 22 +++++++
fs/xfs/scrub/bitmap.h | 19 ++++++
fs/xfs/scrub/rmap.c | 159 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 200 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index ea0725cfb6fb..0b8dfac6d9a3 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -147,6 +147,7 @@ xfs-y += $(addprefix scrub/, \
agheader.o \
alloc.o \
attr.o \
+ bitmap.o \
bmap.o \
btree.o \
common.o \
@@ -170,7 +171,6 @@ xfs-$(CONFIG_XFS_QUOTA) += scrub/quota.o
ifeq ($(CONFIG_XFS_ONLINE_REPAIR),y)
xfs-y += $(addprefix scrub/, \
agheader_repair.o \
- bitmap.o \
repair.o \
)
endif
diff --git a/fs/xfs/scrub/bitmap.c b/fs/xfs/scrub/bitmap.c
index 1b04d2ce020a..14caff0a28ce 100644
--- a/fs/xfs/scrub/bitmap.c
+++ b/fs/xfs/scrub/bitmap.c
@@ -396,3 +396,25 @@ xbitmap_empty(
{
return bitmap->xb_root.rb_root.rb_node == NULL;
}
+
+/* Is the start of the range set or clear? And for how long? */
+bool
+xbitmap_test(
+ struct xbitmap *bitmap,
+ uint64_t start,
+ uint64_t *len)
+{
+ struct xbitmap_node *bn;
+ uint64_t last = start + *len - 1;
+
+ bn = xbitmap_tree_iter_first(&bitmap->xb_root, start, last);
+ if (!bn)
+ return false;
+ if (bn->bn_start <= start) {
+ if (bn->bn_last < last)
+ *len = bn->bn_last - start + 1;
+ return true;
+ }
+ *len = bn->bn_start - start;
+ return false;
+}
diff --git a/fs/xfs/scrub/bitmap.h b/fs/xfs/scrub/bitmap.h
index 7f538effc196..65a6c5a92c7a 100644
--- a/fs/xfs/scrub/bitmap.h
+++ b/fs/xfs/scrub/bitmap.h
@@ -38,6 +38,7 @@ int xbitmap_walk_bits(struct xbitmap *bitmap, xbitmap_walk_bits_fn fn,
void *priv);

bool xbitmap_empty(struct xbitmap *bitmap);
+bool xbitmap_test(struct xbitmap *bitmap, uint64_t start, uint64_t *len);

/* Bitmaps, but for type-checked for xfs_agblock_t */

@@ -65,6 +66,24 @@ static inline int xagb_bitmap_set(struct xagb_bitmap *bitmap,
{
return xbitmap_set(&bitmap->agbitmap, start, len);
}
+static inline bool xagb_bitmap_test(struct xagb_bitmap *bitmap,
+ xfs_agblock_t start, xfs_extlen_t *len)
+{
+ uint64_t biglen = *len;
+ int error;
+
+ error = xbitmap_test(&bitmap->agbitmap, start, &biglen);
+ if (error)
+ return error;
+
+ if (biglen >= UINT_MAX) {
+ ASSERT(0);
+ return -EOVERFLOW;
+ }
+
+ *len = biglen;
+ return 0;
+}

static inline int xagb_bitmap_disunion(struct xagb_bitmap *bitmap,
struct xagb_bitmap *sub)
diff --git a/fs/xfs/scrub/rmap.c b/fs/xfs/scrub/rmap.c
index 3cb92f7ac165..415d8e9918da 100644
--- a/fs/xfs/scrub/rmap.c
+++ b/fs/xfs/scrub/rmap.c
@@ -12,10 +12,12 @@
#include "xfs_btree.h"
#include "xfs_rmap.h"
#include "xfs_refcount.h"
+#include "xfs_ag.h"
+#include "xfs_bit.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/btree.h"
-#include "xfs_ag.h"
+#include "scrub/bitmap.h"

/*
* Set us up to scrub reverse mapping btrees.
@@ -45,6 +47,13 @@ struct xchk_rmap {
* that could be one.
*/
struct xfs_rmap_irec prev_rec;
+
+ /* Bitmaps containing all blocks for each type of AG metadata. */
+ struct xagb_bitmap fs_owned;
+ struct xagb_bitmap log_owned;
+
+ /* Did we complete the AG space metadata bitmaps? */
+ bool bitmaps_complete;
};

/* Cross-reference a rmap against the refcount btree. */
@@ -249,6 +258,68 @@ xchk_rmapbt_check_mergeable(
memcpy(&cr->prev_rec, irec, sizeof(struct xfs_rmap_irec));
}

+/* Compare an rmap for AG metadata against the metadata walk. */
+STATIC int
+xchk_rmapbt_mark_bitmap(
+ struct xchk_btree *bs,
+ struct xchk_rmap *cr,
+ const struct xfs_rmap_irec *irec)
+{
+ struct xfs_scrub *sc = bs->sc;
+ struct xagb_bitmap *bmp = NULL;
+ xfs_extlen_t fsbcount = irec->rm_blockcount;
+
+ /*
+ * Skip corrupt records. It is essential that we detect records in the
+ * btree that cannot overlap but do, flag those as CORRUPT, and skip
+ * the bitmap comparison to avoid generating false XCORRUPT reports.
+ */
+ if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+ return 0;
+
+ /*
+ * If the AG metadata walk didn't complete, there's no point in
+ * comparing against partial results.
+ */
+ if (!cr->bitmaps_complete)
+ return 0;
+
+ switch (irec->rm_owner) {
+ case XFS_RMAP_OWN_FS:
+ bmp = &cr->fs_owned;
+ break;
+ case XFS_RMAP_OWN_LOG:
+ bmp = &cr->log_owned;
+ break;
+ }
+
+ if (!bmp)
+ return 0;
+
+ if (xagb_bitmap_test(bmp, irec->rm_startblock, &fsbcount)) {
+ /*
+ * The start of this reverse mapping corresponds to a set
+ * region in the bitmap. If the mapping covers more area than
+ * the set region, then it covers space that wasn't found by
+ * the AG metadata walk.
+ */
+ if (fsbcount < irec->rm_blockcount)
+ xchk_btree_xref_set_corrupt(bs->sc,
+ bs->sc->sa.rmap_cur, 0);
+ } else {
+ /*
+ * The start of this reverse mapping does not correspond to a
+ * completely set region in the bitmap. The region wasn't
+ * fully set by walking the AG metadata, so this is a
+ * cross-referencing corruption.
+ */
+ xchk_btree_xref_set_corrupt(bs->sc, bs->sc->sa.rmap_cur, 0);
+ }
+
+ /* Unset the region so that we can detect missing rmap records. */
+ return xagb_bitmap_clear(bmp, irec->rm_startblock, irec->rm_blockcount);
+}
+
/* Scrub an rmapbt record. */
STATIC int
xchk_rmapbt_rec(
@@ -268,9 +339,80 @@ xchk_rmapbt_rec(
xchk_rmapbt_check_mergeable(bs, cr, &irec);
xchk_rmapbt_check_overlapping(bs, cr, &irec);
xchk_rmapbt_xref(bs->sc, &irec);
+
+ return xchk_rmapbt_mark_bitmap(bs, cr, &irec);
+}
+
+/*
+ * Set up bitmaps mapping all the AG metadata to compare with the rmapbt
+ * records.
+ */
+STATIC int
+xchk_rmapbt_walk_ag_metadata(
+ struct xfs_scrub *sc,
+ struct xchk_rmap *cr)
+{
+ struct xfs_mount *mp = sc->mp;
+ int error;
+
+ /* OWN_FS: AG headers */
+ error = xagb_bitmap_set(&cr->fs_owned, XFS_SB_BLOCK(mp),
+ XFS_AGFL_BLOCK(mp) - XFS_SB_BLOCK(mp) + 1);
+ if (error)
+ goto out;
+
+ /* OWN_LOG: Internal log */
+ if (xfs_ag_contains_log(mp, sc->sa.pag->pag_agno)) {
+ error = xagb_bitmap_set(&cr->log_owned,
+ XFS_FSB_TO_AGBNO(mp, mp->m_sb.sb_logstart),
+ mp->m_sb.sb_logblocks);
+ if (error)
+ goto out;
+ }
+
+out:
+ /*
+ * If there's an error, set XFAIL and disable the bitmap
+ * cross-referencing checks, but proceed with the scrub anyway.
+ */
+ if (error)
+ xchk_btree_xref_process_error(sc, sc->sa.rmap_cur,
+ sc->sa.rmap_cur->bc_nlevels - 1, &error);
+ else
+ cr->bitmaps_complete = true;
return 0;
}

+/*
+ * Check for set regions in the bitmaps; if there are any, the rmap records do
+ * not describe all the AG metadata.
+ */
+STATIC void
+xchk_rmapbt_check_bitmaps(
+ struct xfs_scrub *sc,
+ struct xchk_rmap *cr)
+{
+ struct xfs_btree_cur *cur = sc->sa.rmap_cur;
+ unsigned int level;
+
+ if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
+ XFS_SCRUB_OFLAG_XFAIL))
+ return;
+ if (!cur)
+ return;
+ level = cur->bc_nlevels - 1;
+
+ /*
+ * Any bitmap with bits still set indicates that the reverse mapping
+ * doesn't cover the entire primary structure.
+ */
+ if (xagb_bitmap_hweight(&cr->fs_owned) != 0)
+ xchk_btree_xref_set_corrupt(sc, cur, level);
+
+ if (xagb_bitmap_hweight(&cr->log_owned) != 0)
+ xchk_btree_xref_set_corrupt(sc, cur, level);
+}
+
/* Scrub the rmap btree for some AG. */
int
xchk_rmapbt(
@@ -283,8 +425,23 @@ xchk_rmapbt(
if (!cr)
return -ENOMEM;

+ xagb_bitmap_init(&cr->fs_owned);
+ xagb_bitmap_init(&cr->log_owned);
+
+ error = xchk_rmapbt_walk_ag_metadata(sc, cr);
+ if (error)
+ goto out;
+
error = xchk_btree(sc, sc->sa.rmap_cur, xchk_rmapbt_rec,
&XFS_RMAP_OINFO_AG, cr);
+ if (error)
+ goto out;
+
+ xchk_rmapbt_check_bitmaps(sc, cr);
+
+out:
+ xagb_bitmap_destroy(&cr->log_owned);
+ xagb_bitmap_destroy(&cr->fs_owned);
kfree(cr);
return error;
}